Her comments reflect a striking shift in public comment by the Obama administration about the violence and come as U.S. officials weigh a large increase in aid to Mexico to help fight the cartels.

Although San Luis Potosi has not been engulfed in the same bloodshed as other states, Naranjo is located on the northeastern edge of the state bordering violent Tamaulipas. Intelligence sources say the Zeta cartel has been steadily moving into that part of the region.

There has been a growing outcry from officials in U.S. border states such as California, Arizona and Texas as the carnage has edged ever closer.

Some U.S. officials are questioning whether their Mexican counterparts are willing to stand up to the cartels as strongly as Colombian authorities. Clinton praised Calderon for his "courage and his commitment" but also called on Mexico to increase its "political will" to fight the cartels.

She said defeating the gangs will require stronger civil, police and military institutions, "married to political will, to be able to prevent this from spreading and beat it back."

In Colombia, billions of dollars in U.S. aid and the policies of hard-line President Alvaro Uribe beat back the FARC rebels. Expanded police ranks have sharply reduced violent crime in the cities. Foreign investment has tripled, fueling a growing economy.

But Plan Colombia has drawn criticism for its heavy use of military force, the presence of hundreds of U.S military advisors and for human rights abuses. The program brought not only the military advisors, but also U.S. special forces personnel and a large numbers of defense contractors.

Clinton acknowledged that Plan Colombia was "controversial … there were problems and there were mistakes. But it worked."

George Grayson, a specialist on Mexico at the College of William & Mary in Virginia, said Clinton's remarks were a sign of U.S. officials' growing alarm at the effects of the drug war.

He said that while President Obama didn't even mention Mexico in his State of the Union message in January, more and more law enforcement and military officials see the situation as a top priority national security threat.

"It's not like Afghanistan or Iran, but it's suddenly on the national security radar," he said.

Even so, he said he was skeptical that Mexico, with its nationalist sensitivities, would consent to a far more active U.S. role, even should Congress be willing to appropriate the funds.

Eric Olson of the Woodrow Wilson International Center for Scholars' Mexico Institute said he senses from conversations with administration officials that "the administration still seems handcuffed by the lack of reliable partners at the operational level."

Olson said that although he was reluctant to be alarmist, "I don't think anybody thinks this has gotten to the bottom."

Administration officials have said in recent days that despite the financial burdens of two other wars, they are considering a sizable increase in spending on the anti-drug war, as well as other improvements to the U.S. counter-narcotics security program.

A White House official who declined to be identified because he was not authorized to speak on the subject said last week that the joint effort with the Mexican government "remains a top administration priority.... We are constantly evaluating our efforts to make sure we are doing all we can on this issue."

U.S. officials have been deliberating for some time how to follow up the Merida Initiative, a three-year, $1.6-billion program started in 2008 by President George W. Bush to provide equipment and training to the Mexican, Central American and Caribbean governments.

paul.richter@latimes.com

ken.dilanian@latimes.com

Staff writer Tracy Wilkinson in Mexico City contributed to this report.